Sickle-cell retinopathy

Sickle-cell hemoglobinopathies are caused by the appearance of one or a complex of abnormal hemoglobins, as a result of which the erythrocytes acquire abnormal form under conditions of hypoxia and acidosis. Deformed erythrocytes are more rigid than healthy cells and can stick together and cause obstruction of small-caliber vessels with subsequent tissue ischemia and marked local acidosis and hypoxia, and even more sickle cells. Sickle cell anemia with mutations of hemoglobins S and C are inherited as alleles of normal hemoglobin A and cause significant complications on the part of the organs of vision.

Abnormal hemoglobin can be combined with normal hemoglobin A in different variants.

1. AS (sickle cell type) occurs in 8% of people with dark skin color. This most mild form is usually accompanied by acute hypoxia.
2. SS (sickle-cell anemia) occurs in 0.4% of people with dark skin color. It causes acute systemic complications with pain syndrome, crises, infarction, and acute hemolytic anemia. Manifestations from the eyes are minor and asymptomatic.
3. SC (sickle cell C with anemia) occurs in 0.2% of people with dark skin color.
4. SThal (sickle cell thalassemia). Both SC and SThal are accompanied by an unexplained anemia with acute ocular manifestations.

[1], [2], [3], [4], [5], [6], [7]

Proliferative sickle cell retinopathy

Most of the acute forms of retinopathy are more often associated with forms of SC and SThal and less often with SS form.

Clinical features of sickle cell retinopathy

Stages of sickle cell retinopathy

• Stage 1. Peripheral occlusion of arterioles.
• Stage 2. Peripheral arteriovenous anastomoses, formed from pre-existing dilated capillaries. The periphery of the retina beyond the area of vascular occlusion is avascular and non-perfusable.
• Stage 3. Growth of new vessels from anastomoses. Initially, the newly formed vessels do not rise above the surface of the retina, have a diffuse configuration, feed from one arteriolus and are drained by a single vein. From 40 to 50% of such sites undergo spontaneous involution as a result of autoinfarctions with the appearance of grayish fibrovascular changes. In other cases, the proliferation of neovascular bundles continues, they contact the cortical vitreous body and can bleed as a result of the formation of vitreoretinal tracts.
• Stage 4. Haemorrhage in the vitreous body after a relatively light eye injury.
• Stage 5. Significant fibrovascular proliferation and traction retinal detachment. Regmatogenic retinal detachment is possible in the case of a rupture near the fibrovascular tissue site.

Foveal angiography reveals extensive areas of lack of capillary perfusion at the periphery of the retina (see Figure 14.926) and later sweating from newly formed vessels.

[8], [9], [10], [11], [12]

Treatment of sickle cell retinopathy

Peripheral photocoagulation of the retina is carried out in the region of absence of capillary perfusion, which causes regression of neovascular tissue in patients with recurrent vitreous hemorrhage. However, in contrast to diabetic retinopathy, new vessels with sickle cell anemia tend to autoinfarcts and spontaneous involution without any treatment.

A vitrectomy of the pars plana with traction detachment of the retina and / or repeated haemorrhage in the vitreous is ineffective.

Non-proliferative sickle cell retinopathy

Asymptomatic disorders

• The tortuosity of the veins, caused by the presence of peripheral arteriovenous shunts, is one of the first eye symptoms.
• The symptom of the "silver wire" of arterioles on the periphery is represented previously by occluded arterioles.
• Pink spots of irregular shape, preretinal or superficial intra-retinal hemorrhages at the equator, near the arterioles, dissolve without a trace.
• "Black radiance" is represented by zones of peripheral hyperplasia of retinal pigment epithelium.
• The symptom of macular depression is represented by the suppression of a bright central macular reflex and is due to atrophy and thinning of the sensory retina.
• Peripheral "holey" rupture of the retina and white spots without "pressure" are observed less often.

Symptomatic disorders

1. Occlusion of paromaculatory arterioles occurs in about 30% of cases.
2. Acute occlusion of the central artery of the retina is rare.
3. Occlusion of retinal veins due to increased viscosity is not typical.
4. Occlusion of choroidal vessels is rare, mainly in children.
5. Angioid retinal bands appear in isolated cases.

Changes outside the retina

Changes in the conjunctiva are characterized by isolated dark red-corkscrew changes in small-caliber vessels that are more often localized in the lower regions.

Changes in the iris are limited areas of atrophy due to ischemia, more often in the pupillary margin, with spread to the ciliary band. Rarely it is observed.